U.S. Pat. Nos. 5,761,115 and 6,487,106 disclose cases in which a programmable metallization cell (PMC) is applied as a solid electrolyte switch of the related art. In a PMC, two electrodes are provided with a solid electrolyte interposed, a suitable amount of metal ions being dissolved in the solid electrolyte. In the working examples in the above-described documents, the solid electrolyte is a construction in which silver ions are introduced into a chalcogenide glass containing germanium or selenium. The solid electrolyte switch is an element for controlling the electrical resistance between the two electrodes by applying voltage between these two electrodes to bring about an oxidation-reduction reaction of the metal ions in the solid electrolyte.
To briefly explain the operation of this solid electrolyte switch, a state of high resistance exists between the two electrodes in the initial state, but when voltage is applied across these two electrodes, the metal ions in the solid electrolyte at one of the electrodes (the cathode side) to which a relative negative voltage is applied are reduced and precipitate as metal atoms. The continuation of the reduction reaction causes the precipitated metal to grow toward the other electrode (the anode) until a metal bridge is finally formed between the two electrodes and an electrical low-resistance state is established between the two electrodes.
On the other hand, when a positive voltage is applied to the cathode side in the state in which the metal bridge is formed, the metal bridge oxidizes and dissolves into the solid electrolyte as metal ions. The electrical high resistance state is reestablished between the electrodes when this metal bridge ceases to exist. The high-resistance state and low-resistance state are each maintained when voltage is not applied, and the solid electrolyte switch therefore is a non-volatile switch with an extremely high ON/OFF ratio, and can be expected to be applicable to non-volatile memory. In addition, the anode also serves the role of a supply source of metal ions, and preferably contains metal that is prone to ionization (such as silver) for the purpose of stable operation.